Proximity-based service (ProSe) communication, also called device-to-device (D2D) or Sidelink communication, is a kind of direct communication between two user equipments (UEs) in Long Term Evolution (LTE) networks. Before a UE transmits ProSe data, the UE should first obtain ProSe resources. There are two modes to allocate ProSe resources: Mode-1 and Mode-2. In Mode-1, the UE sends a ProSe buffer status report (BSR), which includes buffer status of the ProSe logical channels to the evolved NodeB (eNB), and the eNB allocates ProSe resources to the UE per the ProSe BSR. In Mode-2, the UE selects ProSe resources autonomously in a ProSe resource pool.